Generally, unmanned orbital craft use in-situ or in place health monitoring of solar cells. However, bus circuitry in satellites, for example, does not account for in-situ health monitoring of solar cells in the satellite. The bus circuitry of the satellite generally includes dual analog to digital converter (AD) channels and a switchable 28 volt power supply. For in-situ health monitoring of solar cells, measurement of current versus voltage (I-V) curves are performed. To perform measurement of I-V curves, large, high wattage switchable resistor arrays or active current sources are used. However, the large, high wattage switchable resistor arrays or active current sources damage solar cells under test through overdriving.